Delphinium Varieties

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Delphiniums, commonly known as larkspur, feature fan-shaped leaves and flowers with four or five petals. Colors may be blue, lavender, purple, red, pink or white. Several hundred species of perennial and biennial delphinium, in various shapes and sizes, grow in U.S. Department of Agriculture plant hardiness zones 2 to 9, and annual species grow in most areas. Perennial varieties for USDA zones 8 and 9 include scarlet larkspur, candle delphinium, bouquet delphinium and belladonna. Typically growing in fields, gardens and woods, larkspur plants thrive in full to partial sun and organic, well-drained soil. All parts of delphinium plants are poisonous to humans if ingested and it can also poison cats and dogs.

Scarlet Larkspur

Native to the California coast, scarlet larkspur (D. cardinale) grows from 3 to 6 feet tall and about 2 to 3 feet wide. It grows as a perennial in USDA zones 5 to 9. The plant blooms in late May and early June, producing bright red flowers. Scarlet larkspur prefers full sunlight and soil pH of 6.5 to 7.5. Fertilize with an organic or 10-10-10 commercial fertilizer in early spring. Scarlet larkspur attracts aphids, slugs, mites and leaf miners. Possible diseases include fungal leaf spots, powdery mildew and Botrytis blight.

Candle Delphinium

Candle delphinium or candle larkspur (D. elatum) grows in USDA zones 3 to 8. Some plants have dark purple or lavender flowers, while others produce blooms in shades of reds and pinks. Candle delphinium usually grows from 3 to 6 feet tall. However, plants from Pacific Giants, Pacific Coast Hybrids and Pacific Hybrids series grow from 5 to 8 feet tall. The Magic Fountains, Blue Fountains and Blue Springs strains grow only 2 1/2 feet high. Candle larkspur varieties that produce flowers in shades of blue, purple, pink and white include “Blue Jay,” “Galahad,” “Summer Skies” and “Blue Bird.” The Centurion strain blooms within the first year after the seed is sown. It grows to about 5 feet tall and produces large, colorful flowers. When planting in the garden, place candle delphinium stems a couple of feet apart in full sunlight and well-draining soil with a neutral pH of 6.5 to 7.5. Flowers bloom in midsummer.

Bouquet (Chinese) Delphinium

Bouquet delphinium, sometimes called Chinese delphinium (D. grandiflorum) is a thickly spreading perennial that grows about 1 to 2 feet tall. Plants are hardy in USDA zones 4 to 8. The plant typically has dark green leaves and deep blue flowers. Varieties may have blooms in lighter shades of blue, pink and white. Bouquet delphinium cultivars, which grow 8 to 14 inches tall, include “Tom Thumb,” “Dwarf Blue Mirror” and “Blue Butterfly.” Bouquet delphiniums prefer full sun. Like other larkspur cultivars, bouquet delphinium grows well from seed, requiring neutral to alkaline soil with pH of 6.5 to 8.

Belladonna

Belladonna larkspur (D. x belladonna) grows 3 to 4 feet tall and about 2 feet wide. Hardy in USDA zones 3 to 8 or as indoor plants, it has short stems and branched, flaring flower clusters in various shades of blue and white. Flowers grow 1 1/2 to 2 inches wide and bloom throughout the summer. Varieties of belladonna include “Bellamosum,” with dark-blue flowers; “Casablanca,” with white flowers; and “Cliveden Beauty,” which produces flowers in dark turquoise blue. Belladonna larkspurs require neutral to alkaline soil with pH of 6.5 to 8 and partial to full sun.

Growth, Care, Pests and Disease

Garden stores sell potted perennials but you can also grow delphiniums from seed, either in flats or containers. Plant seeds in a potting mix in the summer and you should have flowers in late spring to early summer the following year. Test your garden soil in early fall -- if the pH is too low, add lime to raise it. Transplant the larkspur to the ground, water and fertilize as necessary. Plants need about 1 inch of water per week -- more if weather is extremely dry. Sprinkle 10-10-10 fertilizer on the plants during spring placement into the ground, and again in summer after trimming dead flowers. Delphiniums attract snails, slugs and mites. They are susceptible to root rot, powdery mildew, rust, molds, blight and fungal spots.

About the Author

Teri Silver began a career in 1984 as a news, sports and feature writer/reporter, anchor, editor, producer and program host for central Ohio radio and television stations. She has done work for stations including WTVN, WMNI and WOSU (NPR). Silver has a Bachelor of Arts in journalism with an English minor from The Ohio State University.